The present invention relates to a laminated molding integrated with flexible surface member and a process for manufacturing the laminated molding.
Conventionally, a laminated molding integrated with flexible surface member is used as interior parts of an automobile such as a sun visor and headrest and as an airflow control valve of an automobile air conditioner.
Since a surface of such laminated molding is covered with the flexible surface member, good feel can be obtained in touching by hand.
Further, since a desired cushion property can be obtained by increasing thickness of the surface member, the laminated molding can be used to a component such as a lid of a console box, thus restraining shock sound in opening and shutting and vibration during drive.
Furthermore, since the surface member having cushioning property can seal a gap, good sound insulation and sealing can be given to an airflow control valve when it is applied to an airflow control valve of an automobile air conditioner.
As a process for manufacturing the laminated molding, following manufacturing processes have been conventionally used.
Method A
Manufacturing the laminated molding by attaching the surface member by an adhesive etc. onto a surface of a molding previously manufactured by an injection molding process.
According to the above process, since the surface member has to be attached onto each molding, productivity can be deteriorated on account of work for the attaching process and, furthermore, sufficient attachment strength cannot be obtained by the attaching process with the use of adhesive.
Method B
Filling molten resin between two surface members attached with anti-penetration sheet disposed in a die and press-molding thereof (Japanese Patent Publication No. Hei 2-25806).
According to the above--method, since a nozzle of an extruder has to be advanced and retracted relative to the die for every time filling the molten resin, cycle time for molding one molding product can be lengthened. Further, since the anti-penetration sheet has to be attached to the surface member, manufacturing process can be troublesome.
Method C
After closing a die disposed with two surface members thereinside, injecting and filling molten resin into the die while retaining low pressure and cooling the molten resin to solidify while keeping low dwell pressure (Japanese Patent Publication No. Hei 3-60297).
According to the above method, since the injection pressure is kept relatively low, it requires considerable time to fill the molten resin, thus increasing cycle time, and furthermore, sufficient cushion property cannot be obtained according to material of the surface member.
For solving the problems associated with the respective methods, another method has been proposed (Japanese Patent Application Laid-Open Publication No. 8-127042), where, after a surface member is attached to a molding surface of a compression core on a movable die side, the compression core is advanced to compress the filled molten resin, thus manufacturing a laminated molding integrated with the surface member.
As a material of the surface member, especially for airflow control valve of an air conditioner of an automobile, polyurethane foam is proposed as well as polyethylene foam and polypropylene foam.
According to the manufacturing method of the above invention, cycle time can be reduced without impairing quality of the surface member.
However, though no special problem occurs when the material of the surface member is a foam of polyethylene and polypropylene etc., on account of properties of polyurethane foam different from the other foams, polyurethane foam can be damaged or wrinkled under the same molding condition as the polyethylene etc., a laminated molding having good properties cannot always be obtained.
An object of the present invention is to provide a laminated molding having a surface member made of urethane foam with good properties and a process for manufacturing the same.
A laminated molding according to first aspect of the present invention has a thermoplastic resin base and an ether type urethane foam provided at least one side of the base, the ether type urethane foam mainly made of polyether polyol, which is characterized in that the thermoplastic resin base and the urethane foam are integrally attached by injection compression molding or injection molding under a pressure loading of average pressure relative to project area of a molding cavity of not more than 50 kg/cm2.
The pressure loading refers to a pressure applied to the resin in the die. It refers not only the compression force in the injection compression molding but also includes injection pressure in the injection molding.
The project area of the molding cavity is, in other words, an area of the molding product in a direction orthogonal with open/shut direction of the die.
A laminated molding according to second aspect of the present invention has a thermoplastic resin base and an ester/ether type urethane foam provided at least one side of the base, the ester/ether type urethane foam mainly made of polyester polyol and polyether polyol, which is characterized in that the thermoplastic resin base and the urethane foam are integrally attached by injection compression molding or injection molding under a pressure loading of average pressure relative to project area of a molding cavity of not more than 50 kg/cm2.
The ester/ether type urethane foam includes 10 to 60 wt % of polyester polyol.
The ether type urethane foam and the ester/ether type urethane foam constitute the surface member for the thermoplastic resin base.
The urethane foam can be classified mainly into three types, i.e. ester type urethane foam, ether type urethane foam and ester/ether type urethane foam.
Though the ester type urethane foam is superior in heat resistance, mechanical strength and non-air-permeability, it is hydrolytic and inferior in moist heat aging property. Further, it costs relatively expensive.
Though the ether type urethane foam is not hydrolytic and superior in moist heat aging property, it is inferior in heat resistance and mechanical strength. Further, it cost relatively inexpensive.
The ester/ether type urethane foam is similar to the ether type urethane foam in properties thereof and air permeability (air tightness) can be easily controlled.
Accordingly, since the ether type urethane foam or the ester/ether type urethane foam has characteristics different from the ester type urethane foam, manufacturing condition should be in accordance with the characteristics of the urethane foams.
Specifically, since the ether type urethane foam and the ester/ether type urethane foam are low in heat resistance and strength, when attaching to the base simultaneously with molding step under the same condition as the surface member made of polyester etc, the urethane foams may be broken or wrinkled on account of high temperature and high pressure. Further, the thickness of the urethane foam may be decreased under high temperature and high pressure to lower shock absorption or may be hardened to deteriorate touch thereof.
Accordingly, the present invention has been reached by discovering that, when the urethane foam is ether type or ester/ether type, the above problem of damage on the polyurethane foam can be restrained by integrally attaching the base with the urethane foam under a pressure loading of average pressure of not more than 50 kg/cm2, preferably between 30 to 5 kg/cm2 relative to project area of the molding cavity. The present invention is especially suitable for attaching the ether type urethane foam with the thermoplastic resin base, however, the present invention can also be suitably used for ester/ether type urethane foam.
As a foaming agent of the urethane foam, various foaming agent such as water, flon, methylene chloride etc. can be used.
Though expansion ratio is not restricted, a range of 25 to 100 is appropriate for a sealing member.
Air permeability is preferably not more than 50 cc/cm2/second when it is used for air sealing member such as air-current control valve of an automobile air conditioner. Air sealing property deteriorates when exceeding 50 cc/cm2/second.
Density is preferably 10 to 40 kg/m3. Air permeability can be excessive when density is less than 10 kg/m3 and shock absorption can be insufficient when density is over 40 kg/m3.
Hardness is preferably 5 to 30 kg/200 mmxcfx86. When hardness is less than 5 kg/200 mmxcfx86, air permeability can be excessive and shock absorption can be insufficient when hardness exceeds 30 kg/200 mmxcfx86.
A laminated material integrated with resin film, woven fabric, non-woven fabric on at least one side may be used as the urethane foam.
Though the thermoplastic resin base is not restricted, polyethylene, polypropylene, polystyrene, ABS, polycarbonate, polyamide (nylon) etc. may be used. Various additives such as filler, e.g. talc, calcium carbonate, mica and glass fiber, stabilizer, and coloring agent may be added into the resin base.
Third aspect of the present invention is a method for producing a laminated molding according to first and second aspect of the present invention, which is characterized in that, when the urethane foam is set onto a die and a thermoplastic resin is supplied to the die to integrally attach the thermoplastic resin base with the urethane foam simultaneously with injection compression molding or injection molding, a pressure loading applied to the resin is retained not more than 50 kg/cm2 of average pressure relative to a project area of a molding cavity.
The present aspect of the invention is a method for manufacturing the laminated molding according to first and second aspect of the present invention.
Specific reason etc. of molding condition is the same as described in the first and the second aspect of the present invention.
A method for manufacturing a laminated molding according to fourth aspect of the present invention is, in the third aspect of the invention, characterized in further comprising the steps of: attaching the urethane foam on at least one of molding surfaces of the mutually opposing dies; while keeping the above state, closing the die with a predetermined compression margin retained; filling molten resin onto a side of the urethane foam opposite to another side of the urethane foam in close contact with the molding surface; clamping the die and applying a compression force to the molten resin in the die to pack the molten resin to the entirety of the die; and after packing the molten resin, decreasing the compression force applied to the molten resin.
The present invention shows more specific molding process of the third aspect of the present invention.
The clamping step of the die can be conducted by completely clamping the dies previously incompletely closed, or alternatively, advancing the compression core previously retracted.
According to the present invention, during a step for filling the molten resin, a space larger than the molding product is formed within the die. Therefore, when the molten resin is filled in the die by increasing the injection pressure, since there is a space for the molten resin to be spread in the die, the molten resin filled in the die does not get too much pressure, so that the molten resin does not press the urethane foam with a strong force.
Since the urethane foam is sandwiched by the resin base and the die after completion of packing the resin in the die, the compression force for compressing the die is directly converted into a force for compressing the urethane foam. However, since the compression force by clamping the die is lowered, the urethane foam is not pressed with a great force.
Accordingly, the injection pressure can be increased to fill the molten resin at a high speed, thus reducing cycle time. Further, even when the injection pressure increases, the urethane foam does not break or get wrinkled by being strongly pressed.
A method for producing a laminated molding according to fifth aspect of the present invention is, in the third aspect of the present invention, characterized in having the steps of: attaching the urethane foam on both molding surfaces of the mutually opposing dies; making the dies attached with the urethane foam closer so that the urethane foams touch with each other; while keeping the above state, filling the molten resin between the urethane foams; after the molten resin is filled around a gate for introducing the molten resin into the die, while continuing to fill the molten resin, opening the die to secure a predetermined compression margin; and immediately before or after completion of filling the molten resin, clamping the die and applying a compression force to the molten resin in the die to pack the molten resin to the entirety of the die.
The present invention is a method for manufacturing a laminated molding provided with urethane foam on both sides of the resin base.
Incidentally, when the attached urethane foam blocks the gate for supplying the molten resin, a hole may be opened to the urethane foam on the stationary die side at a position corresponding to the gate, so that the molten resin can be supplied into the die through the hole on the urethane foam.
A method for producing a laminated molding according to sixth aspect of the present invention is, in the fourth and fifth aspect of the present invention, characterized in that the compression force decreased after packing the molten resin in the entirety of the die is re-raised before the molten resin solidifies.
After the surface of the molten resin is cooled to a degree, penetration of the molten resin into the urethane foam or melting of the urethane foam can be restrained, so that a disadvantage such as damage on the urethane foam is not caused even when the compression force of the die is re-raised. Therefore, by re-raising the compression force of the die before the entire molten resin completely solidifies, cooling time of the resin can be shortened without impairing quality of the urethane foam, thereby reducing cycle time.
A method for producing a laminated molding according to seventh aspect of the present invention is, in the third aspect of the present invention, characterized in that the urethane foam is attached onto only one of the molding surfaces of the mutually opposing dies, and that the resin is filled while keeping a cavity clearance between the mutually opposing dies not less than a thickness of the urethane foam under normal temperature and normal pressure and not more than a value adding 20 mm to the thickness.
When the cavity clearance exceeds xe2x80x9cthickness of the urethane foam under normal temperature and normal pressure+20 mmxe2x80x9d, since the die moves excessively during compression step, droop of resin by gravity or insufficient filling and deterioration in appearance on account of increase of internal pressure in the die can be easily generated.
On the contrary, when the cavity clearance is less than xe2x80x9ca thickness of the urethane foam under normal temperature and normal pressurexe2x80x9d, especially when the foam is thin, filling pressure can exceed 50 kg/cm2, so that foam dragging by the resin can be unfavorably occurred.
A method for producing a laminated molding according to eighth aspect of the present invention is, in the third aspect of the present invention, characterized in that the urethane foam is attached onto both molding surfaces of the mutually opposing dies, and that the resin is filled while keeping a cavity clearance between the mutually opposing dies not less than a sum of a thickness of the respective urethane foams under normal temperature and normal pressure and not more than a value adding 20 mm to the sum of the thickness.
When the cavity clearance exceeds xe2x80x9ca sum of thickness of the urethane foams under normal temperature and normal pressure+20 mmxe2x80x9d, since the die moves excessively during compression step, droop of resin by gravity or insufficient filling and deterioration in appearance on account of increase of internal pressure in the die can be easily generated.
On the contrary, when the cavity clearance is less than xe2x80x9ca sum of thickness of the urethane foam under normal temperature and normal pressurexe2x80x9d, especially when the foam is thin, filling pressure can exceed 50 kg/cm2, so that foam dragging by the resin can unfavorably be occurred.
A method for producing a laminated molding according ninth aspect of the present invention is, in the fifth aspect of the present invention, characterized in: that a sum of thickness of the respective urethane foams brought into contact with each other when the mutually opposing dies approaches is set not more than a sum of thickness of the respective urethane foams under normal temperature and normal pressure, and, thereafter, the molten resin is filled between the urethane foams; that, after the molten resin is filled at least around a gate for introducing the molten resin to the die, while continuing to fill the molten resin, the die is opened so that the predetermined compression margin is not less than the sum of thickness of the urethane foam under normal temperature and normal pressure and not more than a value adding 20 mm to the sum; and that the compression force is applied to the molten resin inside the die by clamping the die immediately before or after completion of filling the molten resin to pack the molten resin to the entirety of the dies.
According to the present invention, the two urethane foams are sandwiched between the dies while being compressed before filling and until the molten resin is filled around the gate, so that the position shift of the foam immediately after initiation of filling the resin and underrun of the resin toward backside of the foam (external side of a product) can be securely prevented. When the molten resin is filled around the gate, the die is opened to a predetermined compression margin while continuing to fill the molten resin, so that applied pressure to the urethane foam by the filling pressure of the resin can be reduced, thus easily reducing foam collapsing. Incidentally, limitation of the predetermined compression margin and the effects accompanying thereto is the same as the description of the cavity clearance described in the eighth aspect of the present invention.